The invention pertains to a method for producing rapid setting cement and to the compositions produced therefrom. More specifically, the set time of the cement composition is accelerated through the use of an alkaline activator slurry.
In many instances, it is important to accelerate the setting time of cement mixtures, for example, to rapidly repair or construct highways, airport runways, sidewalks, and the like. All of these tasks require that the cement be poured in place followed by rapid hardening so that the surface can be used again with minimal down time.
The prior art teaches the use of coal fly ash in rapid hardening, cementitious applications where high calcium containing ash is utilized. These ashes are used in combination with both Portland cement and retardants or accelerators, to retard or accelerate the set time of the cement. Variations in setting time in cement compositions comprising fly ash pozzolans and Portland cement have been shown to be achieved by changing the order of introduction of an activator (e.g., citric acid or potassium hydroxide). Additionally, premixing of specific chemicals (e.g., citric acid and fly ash) also has been shown to have an effect on the setting times of cement compositions.